Intel(R) - Computational and Systems Biology at MIT

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7 Intel® Math Kernel Library User’s GuideIn other cases where RTL dependencies might arise, the functions are delivered as sourcecode and it is the responsibility of the user to compile the code with whatever compileremployed.In particular, Fortran 90 modules result in the compiler-specific code generation requiringRTL support, so, Intel MKL delivers these modules as source code.Mixed-language programming with Intel® MKLAppendix A lists the programming languages supported for each Intel MKL functiondomain. However, you can call Intel MKL routines from different language environments.This section explains how to do this using mixed-language programming.Calling LAPACK, BLAS, and CBLAS Routines from C LanguageEnvironmentsNot all Intel MKL function domains support both C and Fortran environments. To use IntelMKL Fortran-style functions in C/C++ environments, you should observe certainconventions, which are discussed for LAPACK and BLAS in the subsections below.LAPACKAs LAPACK routines are Fortran-style, when calling them from C-language programs, makesure that you follow the Fortran-style calling conventions:• Pass variables by 'address' as opposed to pass by 'value'.Function calls is Example 7-1 and Example 7-2 illustrate this.• Store your data Fortran-style, that is, in column-major rather than row-major order.With row-major order, adopted in C, the last array index changes most quickly and thefirst one changes most slowly when traversing the memory segment where the array isstored. With Fortran-style column-major order, the last index changes most slowlywhereas the first one changes most quickly (as illustrated by Figure 7-1 for a 2Darray).7-4
Language-specific Usage Options 7Figure 7-1Column-major order vs. row-major orderFor example, if a two-dimensional matrix A of size m x n is stored densely in aone-dimensional array B, you can access a matrix element like this:A[i][j] = B[i*n+j] in C(i=0, ... , m-1, j=0, ... , n-1)A(i,j) = B(j*m+i) in Fortran (i=1, ... , m, j=1, ... , n).When calling LAPACK routines from C, also mind that LAPACK routine names can be bothupper-case or lower-case, with trailing underscore or not. For example, these names areequivalent: dgetrf, DGETRF, dgetrf_, DGETRF_.BLASBLAS routines are Fortran-style routines. If you call BLAS routines from a C-languageprogram, you must follow the Fortran-style calling conventions:• Pass variables by address as opposed to passing by value.• Store data Fortran-style, that is, in column-major rather than row-major order.Refer to the LAPACK section for details of these conventions. See Example 7-1 on how tocall BLAS routines from C.When calling BLAS routines from C, also mind that BLAS routine names can be bothupper-case and lower-case, with trailing underscore or not. For example, these names areequivalent: dgemm, DGEMM, dgemm_, DGEMM_.CBLASAn alternative for calling BLAS routines from a C-language program is to use the CBLASinterface.7-5
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Intel® Math Kernel Library User’
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Overview 1Intel® Math Kernel Libra
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Intel(R) - Computational and Systems Biology at MIT

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